hydrogen (biohydrogen) is hydrogen produced biologically. The main reactions involve fermentation of sugar derivatives, such as glucose:
A related reaction produces formic acid (leading to the potential for the production of formate derivatives (esters of formic acid) instead of carbon dioxide:
See also: Biohydrogen.
Biomass
Biomass refers to biological material derived from living or recently living organisms, such as plants or plant-derived materials. As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods, which are broadly classified into: (i) thermal, (ii) chemical, and (iii) biochemical methods. This biomass conversion can result in fuel in gas, liquid, or solid form.
Biomass is a renewable energy source unlike other resources such as crude oil, natural gas, tar sand, coal, and oil shale. Agricultural products specifically grown for biofuel production include crops such as corn, soybeans, rapeseed, wheat, sugar beet, sugar cane, palm oil, Jatropha, as well as wood (Table B-14).
Biomass is generally produced in a sustainable manner from water and carbon dioxide by photosynthesis. There are three main categories of biomass—primary, secondary, and tertiary.
Table B-14 Major categories of biomass feedstocks.
| Algae | Prokaryotic algae, Eukaryotic algae, Kelps |
|---|---|
| Aquatic plants | Algae, Water weed, Water hyacinth, Reed and rushes |
| Biorenewable wastes | Agricultural wastes, Crop residues, Mill wood wastes, Urban wood wastes, Urban organic wastes |
| Energy crops | Short rotation woody crops, Herbaceous woody crops, Grasses, Starch crops, Sugar crops, Forage crops, Oilseed crops, Switchgrass, Miscanthus |
| Food crops | Grains, Oil crops |
| Forest products | Wood; Logging residues; Trees, shrubs, and wood residues; Sawdust, bark etc. |
| Landfill | Hazardous waste, Non-hazardous waste, Inert waste, Liquid waste |
| Lichens | Crustose lichens, Foliose lichens, Fruticose lichen |
| Mosses | Bryophyta, Polytrichales |
| Organic waste | Municipal solid waste, Industrial organic wastes, Municipal sewage, and sludge |
Biomass is biological organic matter but is more often used to refer to (i) energy crops grown specifically to be used as fuel, such as fast-growing trees or switch grass, (ii) agricultural residues and by-products, such as straw, sugarcane fiber, and rice hulls, and (iii) residues from forestry, construction, and other wood-processing industries.
Many different types of biomass can be grown for the express purpose of energy production (Table B-15).
Table B-15 Sources, processing options, and uses of biomass-derived products*.
| Resources | Collection | Conversion | End products |
|---|---|---|---|
| Stage 1 | Stage 2 | Stage 3 | Stage 4 |
| Agricultural crops | |||
| Energy crops | |||
| Forestry | |||
| Herbaceous plants | |||
| Oil-bearing plants | |||
| Wastes | |||
| Harvesting | |||
| Handling | |||
| Pretreatment | |||
| Biochemical processes | |||
| Chemical processes | |||
| Physical processes | |||
| Thermochemical | |||
| Biodiesel | |||
| Electrical power | |||
| Heat | |||
| Solid fuels | |||
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